The present invention relates to a discharge device employed in a vehicle that includes an electric circuit having capacitors. More specifically, the present invention relates to a discharge device that forcibly stops electricity supply to the electric circuit when an abnormality related to a collision is detected.
In recent years, in addition to vehicles that use an internal combustion engine as a drive source, there have been proposed hybrid vehicles, which have an internal combustion engine and an electric motor as drive sources, and electric vehicles and fuel cell vehicles, which have only an electric motor as a drive source. Such vehicles have an electric circuit that includes an electric motor for driving the vehicle, a drive circuit for driving the electric motor, and a storage battery for supplying electricity to the drive circuit.
A typical drive circuit has a converter circuit and an inverter circuit. The converter circuit raises the voltage supplied from the storage battery, and outputs the voltage to the inverter circuit. The inverter circuit converts the received direct-current electricity to an alternating-current, and delivers the electricity to the motor. The electric circuit also includes a capacitor for suppressing fluctuation of voltage supplied from the storage battery to the converter circuit and a capacitor for suppressing fluctuation of voltage supplied from the converter circuit to the inverter circuit.
In such vehicles, when an abnormality related to a collision is detected, the connection between the storage battery and the electric circuit is interrupted. This forcibly stops the electricity supply to the drive circuit, thereby stopping the operation of the electric motor.
In addition to such forcible stoppage of electricity supply, forcible discharging of the capacitors in the electric circuit has been proposed so as to prevent leakage from the electric circuit. For example, Japanese Laid-Open Patent Publication No. 2006-141158 discloses an operational control for an electric motor in which, when a vehicle collision is detected, the electric motor is controlled to operate without generating rotational torque. To perform the operational control, the charge (electricity) stored in the capacitors in the electric circuit is used. Through execution of the operational control of the electric motor, the capacitors are discharged. That is, the electricity stored in the electric circuit is released. Accordingly, leakage from the electric circuit is prevented.
To properly discharge the capacitors in the electric circuit in the device disclosed in the above publication, the elements of the electric circuit, such as the converter, the inverters, and the electric motor need to be functioning normally. Therefore, when the drive circuit or the electric motor fails to function due to, for example, a vehicle collision, the operational control of the electric motor cannot be properly executed. Thus, the electric motor cannot adequately consume electricity, and the capacitors therefore cannot be discharged.
Since the capacitors and the electric motor are at positions located away from each other in the device of the above publication, the paths connecting the capacitors and the electric motor to each other tend to be long. The connecting paths are therefore susceptible to influences from vehicle collisions. If any part of the connection paths is broken by the impact of a vehicle collision, the capacitors cannot be discharged.
As described above, according to the device of the publication, whether the capacitors can be discharged or not depends on the operational states of the drive circuit and the electric motor. Therefore, when an abnormality is detected and capacitors are discharged, the reliability of the operation is not necessarily sufficient. Thus, there is still room for improvement in this regard.